Oil in radiator on 2001 BMW 325i

During normal oil service at Jiffy Lube, my mechanic was checking various levels and topping off. When he was checking the radiator he found oil in the water. I checked and sure enough it appears as if the engine is venting oil into the radiator from someplace. Any ideas? A mechanic friend suggested it my be an oil cooler gone bad. Any thoughts and if so any estimate on cost? The car doesn't smoke to I don't believe it is a head gasket.

Asked by for the 2001 BMW 325i
I have this problem in my car now, how did you fix your car?
1 more answer , 1 more comment
Either the power steering oil cooler of engine oil cooler.
None of which i have ever seen leak through, best to have the mechanic look at it.
Surprised they didn't look into it.
Could also be a head gasket. Has to be leaking somewhere where oil and coolant come close to each other.